The influencing of the chronological outflow behaviour of gas generated by a gas generator is of great importance for vehicle occupant restraint systems. For example, it is advantageous for the filling of a gas bag, if the quantity of gas is emitted at least uniformly, viewed over time, or if at the start a smaller and then an increasing gas mass through-flow is made possible. In order to optimize the outflow behaviour, means are therefore used which free or close outflow openings of the gas generator, through which the gas can finally arrive at its destination, during the gas generation phase in line with specific objectives. Such means must operate reliably at high pressures and high temperatures, but at the same time are to be as favourably priced as possible and able to be installed without a great installation expenditure.